Tilt lock device for outboard motor

Abstract

A tilt lock device 10 comprises a cylinder 12, a piston 13 vertically slidably inserted into the cylinder 12, a piston rod 14 connected to an upper portion of the piston 3, upper and lower oil chambers S1 and S2 respectively formed in upper and lower portions of the piston 13, an accumulator chamber S3 mounted to the cylinder 12 in a manner to surround the cylinder 12 and being in communication with the upper and lower oil chambers S1 and S2 through upper and lower oil passages 45 and 12a. A first relief valve 18 is provided in the upper oil passage 45 and is opened when a pressure in the upper oil chamber S1 in which the piston 13 rises exceeds a predetermined value.

What is claimed is: 
     
       1. A tilt lock device for an outboard motor in which said outboard motor is mounted to a stern of a boat and can be stopped at an arbitrary position when it is swung from its in-use position to its stand-by position, the tilt lock apparatus being interposed between said stern and said outboard motor in order to moderate a shock applied to said outboard motor during running, wherein said tilt lock apparatus comprises a cylinder, a piston vertically slidably disposed in said cylinder, a piston rod connected to an upper portion of said piston, upper and lower oil chambers respectively formed in upper and lower portions of said piston, an accumulator chamber surrounding said cylinder and being in communication with said upper and lower oil chambers through upper and lower oil passages, and one or more first relief valves provided in said upper oil passage and being opened when a pressure in said upper oil chamber in which said piston rises exceeds a predetermined value. 
     
     
       2. A tilt lock device for an outboard motor according to claim 1, wherein said accumulator chamber is formed by surrounding said cylinder with an outer cylinder, and a central portion of said outer cylinder is a cylinder having a flat cross-section. 
     
     
       3. A tilt lock device for an outboard motor according to claim 1, wherein said piston is provided with a communication passage for interconnecting said upper and lower oil chambers, said communication passage being provided with a second relief valve which is opened when pressure in said lower oil chamber exceeds a predetermined value, and in a running-ashore state where said piston rises to an intermediate position, if the pressure in said lower oil chamber exceeds the predetermined value, said second relief valve is opened, and said piston is automatically lowered. 
     
     
       4. A tilt lock device for an outboard motor according to claim 1, wherein a cylindrical member is inserted into said accumulator chamber while keeping a predetermined clearance from said cylinder, said accumulator chamber being filled with hydraulic fluid and gas so that a lower end of said cylindrical member always bathes in the hydraulic fluid, and said clearance constitutes said upper oil passage, so that when said first relief valve is opened, gas in said accumulator chamber does not flow back to said upper oil chamber through said upper oil passage. 
     
     
       5. A tilt lock device for an outboard motor according to claim 1, wherein each of said first relief valves comprises a valve body and a spring for pressing said valve body, the spring constants of each of said first relief valves being different from one another. 
     
     
       6. A tilt lock device for an outboard motor according to claim 2, wherein each of said first relief valves comprises a valve body and a spring for pressing said valve body, the spring constants of each of said first relief valves being different from one another. 
     
     
       7. A tilt lock device for an outboard motor according to claim 3, wherein each of said first relief valves comprises a valve body and a spring for pressing said valve body, the spring constants of each of said first relief valves being different from one another. 
     
     
       8. A tilt lock device for an outboard motor according to claim 4, wherein each of said first relief valves comprises a valve body and a spring for pressing said valve body, the spring constants of each of said first relief valves being different from one another.